Buggy code:
public class DefaultProblem implements IProblem , ProblemIrritants , ProblemSeverities { private char [ ] fileName ; private int id ; private int startPosition ; private int endPosition ; private int line ; private int severity ; private String [ ] arguments ; private String message ; public DefaultProblem ( char [ ] originatingFileName , String message , int id , String [ ] stringArguments , int severity , int startPosition , int endPosition , int line ) { } public String errorReportSource ( ICompilationUnit compilationUnit ) { if ( ( ( startPosition ) > ( endPosition ) ) || ( ( ( startPosition ) <= 0 ) && ( ( endPosition ) <= 0 ) ) ) return org . eclipse . jdt . internal . compiler . util . Util . bind ( "problem.noSourceInformation" ) ; final int AROUND = 60 ; final char SPACE = '<seq2seq4repair_space>' ; final char MARK = '^' ; final char TAB = '\t' ; char [ ] source = compilationUnit . getContents ( ) ; int begin = ( ( startPosition ) >= ( source . length ) ) ? ( source . length ) - 1 : startPosition ; int relativeStart = 0 ; int end = ( ( endPosition ) >= ( source . length ) ) ? ( source . length ) - 1 : endPosition ; int relativeEnd = 0 ; label : for ( relativeStart = 0 ; ; relativeStart ++ ) { if ( begin == 0 ) break label ; if ( ( ( source [ ( begin - 1 ) ] ) == '\n' ) || ( ( source [ ( begin - 1 ) ] ) == '\r' ) ) break label ; begin -- ; } label : for ( relativeEnd = 0 ; ; relativeEnd ++ ) { if ( ( end + 1 ) >= ( source . length ) ) break label ; if ( ( ( source [ ( end + 1 ) ] ) == '\r' ) || ( ( source [ ( end + 1 ) ] ) == '\n' ) ) { break label ; } end ++ ; } char [ ] extract = new char [ ( end - begin ) + 1 ] ; System . arraycopy ( source , begin , extract , 0 , extract . length ) ; char c ; int trimLeftIndex = 0 ; while ( ( ( c = extract [ ( trimLeftIndex ++ ) ] ) == TAB ) || ( c == SPACE ) ) { } System . arraycopy ( extract , ( trimLeftIndex - 1 ) , ( extract = new char [ ( ( extract . length ) - trimLeftIndex ) + 1 ] ) , 0 , extract . length ) ; relativeStart -= trimLeftIndex ; int pos = 0 ; char [ ] underneath = new char [ extract . length ] ; for ( int i = 0 ; i <= relativeStart ; i ++ ) { if ( ( extract [ i ] ) == TAB ) { underneath [ ( pos ++ ) ] = TAB ; } else { underneath [ ( pos ++ ) ] = SPACE ; } } for ( int i = startPosition ; i <= ( ( endPosition ) >= ( source . length ) ? ( source . length ) - 1 : endPosition ) ; i ++ ) underneath [ ( pos ++ ) ] = MARK ; System . arraycopy ( underneath , 0 , ( underneath = new char [ pos ] ) , 0 , pos ) ; <START_BUG> return ( ( ( ( org . eclipse . jdt . internal . compiler . util . Util . bind ( "problem.atLine" , String . valueOf ( line ) ) ) + "\n\t" ) + ( new String ( extract ) ) ) + "\n\t" ) + ( new String ( underneath ) ) ; <END_BUG> } public String [ ] getArguments ( ) { } public int getID ( ) { } public String getMessage ( ) { } public char [ ] getOriginatingFileName ( ) { } public int getSeverity ( ) { } public int getSourceEnd ( ) { } public int getSourceLineNumber ( ) { } public int getSourceStart ( ) { } public boolean isError ( ) { } public boolean isWarning ( ) { } public void setSourceEnd ( int sourceEnd ) { } public void setSourceLineNumber ( int lineNumber ) { } public void setSourceStart ( int sourceStart ) { } public String toString ( ) { } }

Fix:
return ( ( ( ( "<seq2seq4repair_space>" + ( org . eclipse . jdt . internal . compiler . util . Util . bind ( "problem.atLine" , String . valueOf ( line ) ) ) ) + "\n\t" ) + ( new String ( extract ) ) ) + "\n\t" ) + ( new String ( underneath ) ) ;